The overall goals of this project are to develop and test reliable, valid methods for detecting drug abusers, characterizing drug use severity and subtyping drug abusers in clinically useful ways. Because the first four years of this project have run concurrently with the DSM-IV revision process, we have focused on issues directly related to suggested revisions and we have met our targeted goals for data collection. In the renewal period, we propose to complete and extend data analyses originally planned and to focus new data collection on one promising aspect of diagnosing drug abusers: psychiatric comorbidity, specifically DSM-III-R/DSM-IV Axis II (Personality) disorders. In the renewal period we propose to 1. Extend data analyses, particularly in the areas of characterizing drug use severity and screening for drug abuse, 2. Give a comprehensive battery of assessments to determine rates of Personality Disorders and their clinical correlates in a. a variety of clinical samples of substance abusers and b. demographically matched community controls, 3. Assess several aspects of reliability and validity of differing systems and methods for diagnosing Personality Disorders/Dimensions in substance abusers, 4. Apply and evaluate methods to enhance the reliability and validity of existing instruments for diagnosing Personality Disorders/Dimensions in substance abusers, and 5. Evaluate the associations among different Personality Disorders in substance abusers and seek underlying dimensions of personality pathology in this special population.